This application is directed to lubricant compositions containing small additive concentrations of phenolic/dimercaptothiadiazole-derived hydroxythioether borates which possess excellent antioxidant properties as well as very good antiwear and extreme pressure/load carrying characteristics.
The use of phenolic compositions such as nonylphenol, and especially hindered phenols, such as di-tertiary butyl paracresol and, has been well-known for imparting antioxidant properties to a variety of lubricant, polymer and elastomer applications.
The use of 2,5-dimercapto 1,3,4-thiadiazole and its derivatives has found widespread application as multifunctional lubricant anticorrision, antiwear, antioxidant and copper passivation additives, see U.S. Pat. Nos. 4,661,273 and 4,584,114.
The use of borate esters has been widely reported as having beneficial multifunctional and friction reducing properties. For example borates and borate esters are disclosed in RE 37,295 and in U.S. Pat. Nos. 4,370,248; 4,298,486 and 4,273,665.
It has now been found that the use of phenolic/dimercaptothiadiazole-derived hydroxythioether borates provides exceptional antioxidant and antiwear/EP activity with potential corrosion inhibiting, antifatigue and high temperature stabilizing properties.